The invention relates to lithium phosphate catalysts. More particularly, the invention relates to lithium phosphate catalysts that have increased activity for the isomerization of alkylene oxide to allylic alcohol.
Lithium phosphate catalyst has been commercially used for the isomerization of propylene oxide to allyl alcohol. The catalyst was first disclosed in U.S. Pat. No. 2,426,264. The catalyst preparation involves precipitating a crude lithium phosphate from the mixture of an aqueous solution that contains phosphate ions and an aqueous solution that contains lithium ions. The crude precipitate is then washed with water and dried to form catalyst powder.
Methods for improving lithium phosphate catalysts are known. For example, U.S. Pat. No. 2,986,585 teaches the use of additional alkali metal hydroxides such as sodium hydroxide and potassium hydroxide during the precipitation of lithium phosphate. Although the function of the additional alkali metals in the lithium phosphate catalyst is not clear, the resultant catalyst has improved activity and selectivity for the alkylene oxide isomerization.
Allyl alcohol has been commercially used as an intermediate for the manufacture of 1,4-butanediol. See U.S. Pat. No. 6,426,437. It has also been increasingly used as a hydroxyl functional monomer in the polymer industry. For instance, allyl alcohol is used for making styrene-allyl alcohol copolymers (see U.S. Pat. No. 5,444,141) and hydroxyl acrylic resins (see U.S. Pat. No. 5,475,073).
It is apparent that improving the lithium phosphate catalyst is important to the industry. Ideally, the catalyst would have increased activity or productivity but would not incur increased cost.
The invention is a method for making lithium phosphate catalysts. The method comprises mixing a first aqueous solution which contains lithium and sodium ions and a second aqueous solution which contains phosphate and borate ions. A precipitate is then isolated from the mixture, and washed and dried to form lithium phosphate catalyst. The catalyst, which contains both boron and sodium, shows increased activity in the isomerization of an alkylene oxide to the corresponding allylic alcohol.